Live Feeds for Marine Fish Larvae

Live Feeds for Marine Fish Larvae

Aquaculture Center for Training, Education and Demonstration

Why live feeds?

This slide shows images of small fish larvae in water, demonstrating the tiny size and delicate nature of marine fish larvae that require live feeds for proper nutrition and development.

This slide shows an image of marine fish larvae, further illustrating the organisms that require live feeds.

Important Criteria For Selecting Live Feeds

• Is it the appropriate size for target species?
• Is the nutritional quality adequate for good growth and survival of the target species?
• Can it be produced cost effectively?

This slide shows three images of marine fish larvae.

Live Feeds

The two live feeds most commonly used are:

Rotifers (Brachionus sp.)
Artemia sp. (brine shrimp)

Other live feeds include: Molluscan trochophore larvae Ciliates

Copepods

Wild plankton

What makes good prey?

Size - prey size is dependent upon fish larvae mouth size. Typical initial prey size for most fish larvae is 50-120 microns in width.

Movement - slow moving prey are more easily captured by fish larvae.

Familiarity - fish larvae must learn to locate and capture prey. The more experience the larvae have with the prey, the higher the success rate.

This slide shows an image illustrating live feed organisms used in marine aquaculture.

Larval Feeding Strategies

Larval fish consume more food per unit body weight (50 – 300%) than fish in grow-out operations (2 – 10%)

Target Densities

1 to 10 prey per ml

Average Feeding Rates

200 to 600 prey per day

Feeding Regime

This chart shows the feeding schedule for fish larvae over a 24-day period (age in days). The feeding regime includes:

• Green water: from 0 to approximately 21 days
• Enriched rotifers: from 0 to approximately 15 days
• Artemia nauplii: from approximately 9 to 24 days
• Enriched Artemia: from approximately 15 to 24 days
• Microfeeds: from approximately 18 to 24 days

The x-axis shows age in days (0, 3, 6, 9, 12, 15, 18, 21, 24) and the different feed types are represented as horizontal bars across the timeline.

Rotifers

Image of Rotifer

Why use rotifers as live food?

Excellent for larval fish and shellfish

• High nutritional quality
• Small body size
• Slow swimming rate
• High rate of reproduction
• Low rate of mortality

What is a Rotifer?

• Microscopic protozoan
• Saltwater and fresh water environments
• Asexual and sexual reproduction

Phylum Rotifera "wheel-bearer" (> 2000 species)

Rotifer Corona

Cilia

This slide shows a microscope image of a rotifer with the corona (wheel-like structure) clearly visible, surrounded by cilia that create a rotating appearance when in motion.

Planktonic rotifers swim continuously and rarely attach. The foot is used to attach when needed. At the base of the foot are the toes used to attach to the substrate.

Foot

Toes

This slide shows a microscope image of a rotifer with labels pointing to the foot and toes at the bottom of the organism.

Species & Strains

Marine Species

Brachionus plicatilis Brachionus rotundiformis

Freshwater

Brachionus rubens Brachionus calycflorus

Three Strains

L-type (large type, B. plicatilis)

Body length = 200 - 360 µm

S-type (small type , B. rotundiformis)

Body length = 150 - 220 µm

SS-type (special small, B. rotundiformis)

Body length = 70 - 160 µm

Optimal Conditions

Salinity below 35 ppt

Temperature range 27- 32°C

15 hour photoperiod

Moderate to low aeration

pH range from 6.5 - 8.0

Unionized ammonia concentrations: not to exceed 1 mg/liter

When the conditions are right

Female with eggs

Juvenile

This slide shows a microscope image of a female rotifer with visible eggs inside her body, demonstrating successful reproduction when environmental conditions are optimal.

Production Methods

• Cultures can be started by inoculations with live rotifers or by using cysts (resting eggs)
• Cysts have a shelf life of over one year
• Rotifers can be produced using algae, yeast, specialized products, or a combination
• Acceptable rotifer production ranges from 100 - 500 per ml
• Super-intensive culture requires specialized labor, equipment and techniques

Culture Methods

Continuous

Lasts 20 to 30 days

Harvest 20 to 30% per day

Refill with sterilized water daily

Batch (Our Method)

Harvest all rotifers at 3 to 5 days

Discard water

Re-stock with new water and rotifers

Intensive Production Methods

Requires:

• Continuous supply of algae
• De-foaming agents
• Filtration of water
• pH adjustments
• Oxygen gas
• Nylon filtration mats

Diligent & Constant Management!

Inside Rotifer Tank

This slide shows a photograph of the interior of a rotifer culture tank, displaying the water surface and culture equipment used in rotifer production.

This slide shows a photograph of rotifer culture equipment and facilities used in the production process.

Culture Condition

Rotifer cultures are healthy if:

• Rotifers are swimming rapidly
• Females with eggs : female ratio of about 1.2 :1
• Little or no bacteria or ciliates present

Cloudy water is a good sign of imminent crash

Crashing cultures will have a bad odor

This slide shows a photograph of rotifer culture tanks and equipment used in the production facility.

Our Rotifer Formula

Fill tank with seawater adjusted to 25 - 35 ppt

Add liquid chlorine (10%) & mix

Add sodium thiosulfate to neutralize chlorine and areate.

Add inoculating rotifers - a minimum of 150 to 250 per ml

Production Methods

Use light aeration

Keep light intensity to a minimum

Feed live algae/algae paste and rotifer diet daily

After 3 - 5 days rotifers will reach 500 to 750 per ml

Harvest and enrich for feeding and use to inoculate new tanks

Feeding Algae

Nannochloropsis oculata & Isochrysis galbana

Instant Algae

Live Algae

This slide includes images of commercial algae products used for feeding rotifers.

Rotifer Diets

This slide shows a photograph of various commercial rotifer diet products used in aquaculture facilities.

Rotifer Enrichment

Bioencapsulation – feed rotifers nutrients essential for larval fish

Enrichment increases the Omega 3 fatty acids in the rotifers.

Common enrichment products:

• Algae - live, frozen, or dried
• Emulsion products - liquid or dry
• Selco (culture and DHA protein), Microfeast, Algamac, RotiRich

Enrichment

What??

Why??

Fatty Acids

Amino acids

Vitamins

Pigments

Probiotics

Enrichments

20 million rotifers (10 am)

Water bath (28 °C) for 3 h

Harvesting

This flow chart shows the first steps of the enrichment process with arrows connecting each step.

Cold storage (5-10 °C)

This slide shows the final step of the enrichment process flow chart.

Rotifer Schedule

Artemia

Photograph of Aremia salina

What is an Artemia?

Microscopic crustacean (brine shrimp)

Saltwater environments

Sold as cysts

This slide shows images of Artemia organisms used as live feeds in aquaculture.

Decapsulation

This diagram shows the decapsulation process:

Dehydrated cysts

Hydrated cysts

+ chemicals

The slide includes microscope images showing the different stages of the cysts.

Decapsulated cysts

This slide shows a microscope image of decapsulated Artemia cysts, which appear orange/light colored without their outer shell after chemical treatment.

Incubation

Sterilized water

25-30 g/L salinity

28-30 C

Vigorous aeration

15-20 h = hatching

"Umbrellas"

First instar

This slide shows microscope images of Artemia during hatching. The "umbrellas" are the empty cyst shells that float to the surface after hatching. The first instar nauplii are the newly hatched Artemia that appear 15-20 hours after incubation begins.

This slide shows a tank and equipment related to Artemia culture and production.

This slide shows a tank related to Artemia culture and production.

This slide shows images related to Artemia culture and production.

Enrichment

Second instar

This slide shows a microscope image of second instar Artemia nauplii, which are larger and more developed than first instar nauplii.

This slide shows images related to the Artemia enrichment process.

Sterilized water

25-30 g/L salinity

26-27 C

Moderate aeration

Enrichment contact 24 hrs.

This slide shows an image related to the Artemia enrichment process.

Artemia Schedule

Feedings should be spaced out during 24 period ~ 4-6 hrs.

This is the final slide of the presentation showing microscopic image of Artemia.